DEPARTMENT OE MARINE BIOLOGY. I39 



under favorable conditions of growth may attain a length of 200 mm. in 

 three years ; and with a subsequent annual increase of 50 to 100 mm., a maxi- 

 mum diameter of 300 mm. would represent four to five years ; 400 mm., five 

 to seven years ; 500 mm., six to nine years. Ten years' growth would pro- 

 duce a large corallum. Should the environment be unfavorable, a colony 

 may increase only slightly in size. 



In 1910 the number of records for M. clivosa was increased to 16. 



Manicina ("Colpophyllia') gyrosa. — Two specimens are being annually 

 measured. One of them was transferred from a pier of the Fort Jefferson 

 dock and planted in the moat near the southeast exit in 1908. A mistake 

 was made in the identification of this coral, while its skeleton was covered by 

 living soft tissue, and in the reports for 1908 and 1909 it is referred to as 

 Mccandra labyrinthiformis* Its length in 1908 was 65 mm.; in 1909, 

 85 mm. ; in 1910, 122 mm. ; an increase of 88 per cent in two years. Its 

 breadth in 1908 was 65 mm. ; in 1909, 85 mm. ; in 1910, 112 mm. ; an increase 

 of J2, per cent in two years. Its height in 1908 was 20 mm. ; in 1910, 32 

 mm. ; an increase of 60 per cent in two years. 



The other specimen, which is attached to a pier of the Fort Jefferson dock 

 and is shaded above by an Oculina colony, seems to have grown but little. 

 In 1909 it had a maximum diameter of 144 mm. (erroneously given as 154 

 mm. in the report of 1909) ; in 1910 diameter in horizontal plane 147 mm. ; 

 in vertical plane 132 mm. ; thickness 55 mm. 



Siderastrea radians. — Seven colonies living in the moat were measured in 

 1909 ; of these, in 19 10 two were apparently dead ; two others had grown but 

 little, while the three others had increased in length and breadth, the range 

 of increase being from 21 to 46 per cent. The largest of these colonies now 

 has a length of 58 mm. ; all are therefore small. The growth rate as com- 

 pared with other species is slow and the colonies appear not to be thriving. 

 Exposure at low tide is probably the principal disadvantageous factor. 



In 1910 the number of records was increased to 10; six of the specimens 

 are cemented to tiles planted off the northwest face of the Fort Jefferson 

 moat wall and are permanently below water-level. 



Agaricia sp., probably fragiUs var. — Previous to 1910 only one colony was 

 measured. It was attached to a pier of the Fort Jefferson dock, but was 

 knocked off between the summer of 1909 and 1910. It was an attached thin 

 plate, and showed between 1908 and 1909 an increase in length from 50 to 

 69 mm. or 38 per cent ; in width from 37 to 54 mm. or 46 per cent. 



In 1910, 10 new records were initiated upon this species of Agaricia. 



Poritcs clavaria. — Two colonies growing in the moat were measured in 

 1909 and again in 1910, but the data are not satisfactory. The increase in 

 length and breadth ranged from 54 to 100 per cent ; that in height from 10 

 to 43 per cent. The growth rate under favorable conditions is evidently rapid. 



In 1910 the records upon Pontes clavaria were increased to 8. 



Porites furcata. — Thirteen colonies, two attached to piers of the Fort Jef- 

 ferson dock and eleven living in the moat, were measured in 1909. Of this 

 number, two colonies in the moat had not grown or had been damaged, while 

 the remaining eleven furnished interesting information. As the table em- 

 bodying the data is long, it will not be inserted here, but remarks on it will be 

 made. 



* Carnegie Institution of Washington, Year Book No. 7, 1908, p. 135 ; Year Book No. 

 8, 1909, p. 142. 



